I tend to have these images running through my mind that are so vivid that they almost seem like memories. Could it mean anything? Or do I just have ab over-active imagination? Might sound like a stupid question, but I can't help but wonder sometimes.

I don't think it is a stupid question at all. In fact, I think it shows great wisdom and responsibility. You are not assuming that they are from a spiritual or magical source. Many would, and not think twice about it.

Without more information, I really couldn't say what it is. No one can. We are not you. I would say write them down. Maybe they will reveal their meaning over time. At the same time, I would not give them extra thought. If they are products of imagination, focusing on them and giving them energy could produce delusions or other psychological problems. Study and grow, and you will find the answer.